It is desirable to operate the engine at temperatures as close to the limits imposed by oil properties and strength of the materials as possible. Removing too much heat through the cylinder walls and head lowers engine thermal efficiency. However, prior art cooling systems have tended to overcool in some zones and undercool in others; the prior art systems have been a rough compromise designed to remove approximately 30 to 35% of the heat produced in the combustion chambers resulting from the combustion of an air-fuel mixture. The systems have typically been of the forced circulation type utilizing a water jacket placed around the engine cylinders. Through the years, the water jacket has evolved as an immensely intricate casting with intersecting channels and intersecting bosses delicately cored within the metal casting. Principal emphasis has been to allow water to circulate freely within a bath adjacent the cylinders and head valves. On some engines, water distributing tubes or nozzles have been used to direct the flow of the cooling water into the water jacket reservoir in the hopes of regulating heat transfer. Because of the need to extend bolts, shafts and shanks through the water jacket cavity, flow therein is interrupted and detrimentally affected. The water jacket has now become a labyrinth of passages which do not contribute to controlled fluid flow.
The need to improve the cooling system, increase fuel economy, and economize on the use of cast material has only recently become acute. Prior to this there was greater emphasis given to ease of casting and the benefit of having a large safety factor in block strength by making the engine block large and relatively heavy. Now there is a clear necessity to reduce the weight of the engine, utilize less casting material, while at the same time increase the efficiency of the cooling system.
To economize on weight as well as improve thermal efficiency, several problems must be simultaneously overcome, including: (a) elimination of turbulent cooling flow within the engine block resulting from improper passage wall design; (b) design and cast thinner wall sections throughout the engine, which sections are more closely designed to the material strength limit thereby eliminating excess weight; (c) substitute lighter materials having a higher thermal conductivity without sacrificing strength; and (d) reduce the volume and thereby the weight of cooling fluid while still maintaining a uniform engine wall temperature. These problems of flow, thickness, material and fluid volume must be overcome together.